The present invention generally relates to a data processing apparatus and a power supply controller.
These years, since a strong demand is directed to making small data processing apparatuses (data processors) in size and thickness, a liquid crystal type display has been recently increasingly employed as a display.
In some of such data processing apparatuses, for the purpose of improving the miniaturization and operating convenience, the back light brightness is set on a software basis.
Further, for the purpose of lengthening the operating time of a battery to meet a cordless demand, there have been suggested various devices to suppress consumption power.
In a liquid crystal back light controller disclosed in, for example, JP-A-2-4221, a light receiving hole having an opening is provided in the liquid crystal display side of a liquid crystal holder, a light receiving element for sensing visible light is provided at the bottom of the light receiving hole, and a controller is provided for controlling the turning ON and OFF of back light on the basis of an output signal of the light receiving signal to control the back light.
Further, it has been conventionally common practice to supply power to respective devices built in a single unit at the same time.
This will be detailed by referring to FIG. 13. The drawing shows waveforms of a consumption current for a back light and a consumption current for other devices of the system as well as a total of these two consumption currents with respect to the ON and OFF states of a power supply switch, with ordinate axis denoting consumption current and abscissa axis denoting time.
As will be appreciated, since the supply of power to the back light and the supply of power to the other devices are started at the same time in the prior art, the peak values of these consumption currents take place at the same time. This results in that a maximum peak current I.sub.pl corresponding to a total of these consumption currents becomes (I.sub.pb +I.sub.pd) (where I.sub.pl denotes the maximum peak value of the total consumption current in the prior art, I.sub.pb denotes the peak consumption current value for the back light, and I.sub.pd denotes the peak consumption current value for the other devices), which is very large.